>> president obama will be in boston tomorrow to help there. vigils of course going all over, a vigil, last night in boston common not far from the bombing scene. >> that's right. two vigils one was for martin, the 8-year-old. another one that was for everybody who was hurt, who was killed, who was there, who just need to come together and be part of a community in moments like this. understandably they wanted to support each other. in times like this that's what is needed. >> harvard, boston university planning vigils. >> there will be more, i am sure. >>> all right, as the search for clues continues in boston, diane sawyer sat down with one man who knows all too well what it feels look to lead a city under attack. former new york city mayor rudy giuliani said we still don't know how much evidence was caught on camera. >> they have a lot of surveillance cameras in boston. more than new york. less than london. you have very much focused on event with the lives of people. professional cameras, amateur cameras. it may be that some person photogra